Method for preparing polyurethane foams

ABSTRACT

The invention relates to organopolysiloxane foam stabilizers for polyurethane foams which are obtained from the hydrolysis of mixtures of (a) silanes of the formula RnSiX4 n and (b) silanes of the formula R3SiX in which R is a hydrocarbon radical, X is a hydrolyzable group and n is 0 or 1.

United States Patent 1191 1111 3,839,242 Huber et al. Oct. 1, 1974 [54} METHOD FOR PREPARING 3,703,486 12/1972 K6 260 25 AH POLYURETHANE FOAMS 3,706,681 12/1972 Bachura 260/25 AH 3,741,917 6/1973 Morehouse 1 Inventors: Peter Huber; Ewald Pirson, both of 3,772,224 11/1973 M6111 260/25 AH Burghausen Germany FOREIGN PATENTS OR APPLICATIONS [731 Asslgnee? wacker'chemil GmbH, Mumch 720,212 2 1969 Belgium 260/25 AH Germany 294,430 11/1971 Austria l22| Filed: Sept. 26, 1973 Primary ExaminerM. J. Welsh [2H Appl' 400875 Assistant Examiner- C. Warren Ivy [30] F orelgn Application Priority Data 57] ABSTRACT- Sept. 21. 1972 Germany 2246400 [52] US. Cl....260/2.5 AH, 260/25 AP, 260/25 AZ, The invention relates to organopolysiloxane foam sta- 260/448.2 R bilizers for polyurethane foams which are obtained [51] Int. Cl C08g 22/44 from the hydro ysis of xt of silanes of th [58] Field of Search 260/25 AH, 2.5 AP, 2.5 AZ formula R,,SiX and (b) silanes of the formula R SiX in which R is a hydrocarbon radical, X is a hydrolyz- [56] References Cited able group and n is O or 1.

UNITED STATES PATENTS 8/1968 Windemuth 260/25 AH 12 Claims, No Drawings METHOD FOR PREPARING POLYURETHANE FOAMS foamed products may be controlled or modified by carrying out the foaming reaction in the presence of silicone oils or polysiloxanes of relatively high molecular weights, for example of up to 20,000. The addition of such polysiloxanes, which have a viscosity of at least centistokes at 25C. facilitates the production of foams with a uniform fine pore structure. However, certain disadvantages are associated with the use of this particular type of polysiloxane. Thus for example when such polysiloxanes are used in the preparation of foams from pre-formed polyether-polyisocyanate reaction productsor prepolymers, in particular by reaction with wa ter, the foamed products frequently shrink owing to the presence of an excessively high proportion of closed cells. This tendency to shrink is especially marked in foams of considerable thickness, for example over 12 inches thick. Such foams are difficult to treat by the crushing procedure usually required to break closed cells. Another common method for the preparation of foams comprises the reaction of polyethers and polyisocyanates in the presence of gas-forming materials such as water. The use of the relatively high molecular weight polysiloxanes in this method of preparation or in the alternative prepolymer method already referred to, is frequently ineffective since these polysiloxanes do not always stabilize the foaming mixtures sufficiently to prevent the loss of appreciable quantities of gas and the consequent formation of comparatively high density products.

Thus it is an object of this invention to provide a polyurethane foam having uniform cells. Another object of this invention is to provide a polyurethane foam which is substantially free of shrinkage. A still further object of this invention is to provide a polyurethane foam having a soft skin with sub-surface bubbles. A further object of this invention is to provide organopolysiloxanes which are stabilizers for polyurethane foams. Still a further object of this invention is to provide a method for preparing stable polyurethane foams.

The foregoing objects and others which will become apparent from the following description are accomplished in accordance with this invention, generally speaking, by providing an improved method for the preparation of polyurethane foams by the reaction of a substance having active hydrogen atoms as determined by the Zerewitinoff method with an organic polyisocyanate in the presence of a blowing agent, catalyst, cross-linking agent and foam stabilizing agents.

The foam stabilizing agents of this invention are organopolysiloxanes which are obtained from the hydrolysis of mixtures of (a) silanes of the formula R,,SiX and (b) at least 1 mol equivalent for each X in the silanes (a) of silanes of the general formula R;,SiX, where R is a hydrocarbon radical, X is a hydrolyzable group and n is 0 or 1. The organopolysiloxanes thus obtained have a boiling point below about 200C. at 0.1 mm Hg (abs).

The hydrocarbon radicals represented by R above are aliphatic hydrocarbon radicals having from 1 to 18 carbon atoms and aromatic hydrocarbon radicals. Suitable examples of aliphatic hydrocarbon radicals are alkyl radicals suchas methyl, ethyl, propyl, butyl, tetradecyl and octadecyl radicals. Examples of suitable aromatic hydrocarbon radicals are aryl radicals such as phenyl.

In silanes of the formula RSiX it is preferred that the R group be phenyl, whereas in silanes of the formula R SiX, it is preferred that the R group be methyl.

The hydrolyzable groups represented by X may be halide atoms, such as chlorine, bromine, iodine and fluorine; alkoxy groups having from 1 to 8 carbon atoms such as methoxy, ethoxy, butoxy, heptoxy and octoxy radicals; monoacyl radicals of carboxylic acids such as acetoxy, propionyloxy, valeryloxy, caproyloxy, myristoyloxy and stearoyloxy radicals and hydrogen. The types of hydrolyzable groups are not critical since these groups are split off during hydrolysis and the resulting by-products containing these groups are easily removed from the hydrolysates. However, chlorine is the preferred hydrolyzable group because of its availability. In both types of silanes (a) and (b) the R groups and the hydrolyzable groups X may be the same or different. y

In the preparation of the organopolysiloxane hydrolysates, mixtures of one type or the otherof silanes (a) and (b), mixtures of more than one type of silanes (a) as well as only one type of silanes (b), mixtures of only one type of silanes (a) and more than one type of silanes (b), as well as mixtures of more than one type of silanes (a) and (b) may be used.

When at least 1 mol of silane (b) is used per equivalent of X of silane (a), the resulting hydrolysatesare linear or branched organopolysiloxanes. a In order to obtain the highest yield of hydrolysates having a boiling point below about 200C. at 0.1 mm Hg (abs.), it is preferred that n have a value of 1. For the same reason it is preferred that at least 1% mol of silane (b) be employed for each X equivalent in silanes (a) in the production of the organopolysiloxanes of this invention.

Although it is not critical, it is preferred that the Si lane mixtures from which the hydrolysates of this in vention are prepared, contain a maximum of 3 mols of silane (b) for each X equivalent of silanes (a).

Thus the hydrolysates which are employed in accordance with this invention are preferably prepared from phenyltrichlorosilane and trimethylchlorosilane at a mol ratio of 1:4v to 1:12 and more preferably at a mol ratio of 1:6 to 1:10. 7

Hydrolysates obtained from tetradecyltrichlorosilane and trimethylchlorosilane at a mol ratio of l to atleast preferably omitted. It is however, advantageous to neutralize the hydrolysates prior to their use as foam stabilizers in urethane compositions. They may be neutralized, for example by washing with water, since they contain acids or bases.

Although it is not essential, it is preferred that the hydrolysates be separated from components which have a boiling point higher than 200C. at 0.1 mm Hg (abs) as well as from siloxanes corresponding to the formula (R Si) O, if indicated. This may be accomplished by distilling off the hydrolysates from the non-distillable components or from components which have a boiling point above 200C. at 0.1 mm Hg (abs). The resulting hydrolysates may be employed in the same amount as conventional organosilicone compounds which have been used as foam stabilizers heretofore in manufacturing polyurethane foam plastics from polyethers having an average of at least two hydroxyl groups per molecule and organic diisocyanates in the presence of interlinking agents, catalysts and water and/or foaming agents such as hydrocarbons. Generally these amounts range from about 0.2 to 1.3 parts by weight of hydrolysate for each 100 parts by weight of polyether.

The process of this invention is important in polyether cold foam systems. (The term cold foam systems or cold foam is described in Plaste and Kautschuk, Vol. 17, pp 887/888. Cold foam systems are also referred to as cold foaming of polyurethane foam in DT-AS 20,14,01 l and in the Anglo-Saxon literature as cold molded urethane flexible foam," as indicated' in Journal of Cellular Plastics May/June 1972, p 134). The organosilicone compounds which have been used heretofore as foam stabilizers in polyether cold foam systems, did not produce foams which have both fine as well as open cells, because when the foams attained the largest foam volume they hardened to such an extent that these organosilicone compounds could no longer open the cell walls.

In cold foam systems the polyethers may be branched or linear and have hydroxyl groups per molecule in which the ratio of the primary hydroxyl groups tothe secondary hydroxyl groups is mostly at least 50:50; but can be up to 85:15.

Examples of suitable polyethers for use in the process of the present invention include those polyethers disclosed as suitable for the preparation of polyurethane foams in the prior art,-such as polymers having terminal hydroxy groups and co-polymers of cyclic oxides such as 1,2-alkylene oxides for example ethylene oxide, epichlorhydrin, 1,2-propylene oxide, and 1,2- and 2,3- butylene oxides, oxacyclobuta'nes and tetrahydrofuran. Thus suitable polyethers may be prepared by polymerizing by the general methods described in the prior art one or more cyclic oxides in the presence of a difunctional compound containing two reactive hydrogen atoms per molecule, such as water, a glycol or a primary monoamine, or in the presence of a polyfunctional compound containing more than two reactive hydrogen atoms per molecule, such as ammonia, a monoalkanolamine, a polyamine or a polyhydroxy compound, for example a trihydric alcohol such as glycerol, a sugar such as sorbitol, or a phenol/formaldehyde reaction product. The process of the present invention is particularly advantageous when applied to hydroxyl-ended polyethers of molecular weights from 1000 to' 8000, preferably from 1500 to 6000.

Especially valuable are the polyethers obtained by polymerisation of 1,2-propylene oxide, 12- and 2,3-

butylene oxide or mixtures of these oxides with each other and/or with minor proportions of other alkylene oxides such as ethylene oxide.

Suitable organic polyisocyanates for use in the process of the present invention include polyisocyanates described in the prior art as suitable for use in the preparation of polyurethane foams. Examples of suitable organic polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate, aromatic diisocyanates such as tolylene-2,4-diisocyanate, tolylene-2,6- diisocyanate, diphenylmethane-4,4-diisocyanate, 3- methyldiphenylmethane-4,4-diisocyanate, mand pphenylene diisocyanate, chlorophenylene-2,4- diisocyanate, naphthylene-l,5-diisocyanate, diphenyl- 4,4-diisocyanate, 4,4-diisocyanato-3 ,3 dimethyldiphenyl and diphenyl ether diisocyanate and cycloaliphatic diisocyanates such as dicyclohexylmethane diisocyanate. Triisocyanates which may be used include aromatic triisocyanates such as 2,4,6- triisocyanatotoluene and 2,4,4-triisocyanatodiphenyl ether. Examples of other suitable organic polyisocyanates comprise the reaction products of an excess of a diisocyanate with polyhydric alcohols such as trimethylolpropane, and uretedione dimers and isocyanurate polymers of diisocyanates for example of tolylene-2,4- diisocyanate. Mixtures of polyisocyanates may be used. Examples of suitable mixtures include the polyisocyanate compositions obtained by the phosgenation of the mixed polyamine reaction products of formaldehyde and one or more aromatic amines such as aniline and orthotoluidine.

Generally the organic diisocyanates in the cold foam systems are mixtures of from30 to 70 weight percent diphenyl-methane-p,p'-diisocyanate and 70 to 30 weight percent tolylene diisocyanate-isomers.

Examples of suitable cross-linking agents are 1,4- butandiol, 2,3-butandiol, triethanolamine, neopentylglycol, trimethylolpropane, 3 ,3 -dichloro-4,4 diaminodiphenylmethane and the compound represented by the formula CH CH C(CH OCH CH OH) The cross-linking agents are preferably employed in amounts of from 1 to 5 parts by weight for each 100 parts by weight of polyether having on the average at least two hydroxyl groups per molecule.

Catalysts which may be used in the formation of urethane foams are the amino compounds such as triethylenediamine, N,N,N',N-tetramethyl- 1,33-butanediamine, thylenediamine, dimethylethanolamine, dimethylcyclohexylamine, triethylamine, dimethylpiperazine and N-methylmorpholine. Other basic compounds which may be used as catalysts are alkali metal hydroxide or a salt of a weak acid such as carbonate or acetate, or a non-basic heavy metal compound such as dibutyl tin dilaurate or manganese acetyl acetonate or stannous octoate.

The formation of the foamed products of this invention may be accomplished by reacting the polyether with excess polyfunctional isocyanates in the presence of water. The water may be used in various amounts according to the density of foamed product required but it is normally incorporated in an amount of from l per cent to 10 percent by weight of polyether. The water may be used as the sole gas-forming agent or may be replaced wholly or in part by a non-isocyanate-reactive volatile liquid having a boiling point not greater than about C., and preferably from 40C. to 50C., for example halogenated hydrocarbons, in particular fluorinated alkanes such as monofluorotrichloromethane,

dibromoclifluoromethane and l ,1 ,2-trichloro-1,2,2- trifluoroethane.

The process of the present invention may be carried out by the general methods more fully described in the a short period of time, the aqueous phase is removed and the hydrolysateis washed with 200 parts of water until the rinsing water has a pH of 7. After distilling the hydrolysate at 10 mm Hg (abs), about 280 parts of a prior art relating to the manufacture of foamed poly- 5 colorless liquid is recovered; urethanes. Thus the'polyether may first be converted to (b) The Procedure e (a) abeve is a polyether polyiso'cyanate prepolymer by reaction in peated, except that the silane mixture consists of 211 one or more stages with an amount of polyisocyanate Parts of Phehyltriehleresilane and 972 Parts of trimein excess of the amount equivalent to the hydroxyl endthllehlel'oshahe- After distilling the hydrolysate at 5 groups of the polyether. The preparation of the pre- 10 mm Hg about 600 Parts of a colorless liquid is polymer may be carried out by heating the polyether o e ed and polyisocyanate together at for example 75 to COMPARISON EXAMPLE l25C., or by allowing the two materials to react with- (c) The procedure described in (a) above is repeated out appheaheh of exfemal heat the P s a except that the silane mixture consists of 260 parts of catalyst for the reaction, for example a tertiary amine dimethyldichlorosilane and 324 parts f trimethy]- or a nonbasc heavy metal compound Such as mange chlorosilane. Distillation was carried out at 160C. at nese acetylacetonate. The prepolymer may then be 12 mm Hg (abs due to the low boiling point of the f l foam by the gaS'fOFmmg drolysate. About 200 parts of a colorless liquid is rematerial, if deslred with the addition of more polylsocycovered anate. Alternatively the polyether, polyisocyanate and 0 gas-forming material such as water may be interacted PLE 2 T0 6 simultaneously to produce the foam in a single stage. In a 2 liter beaker are placed about:

e descnbed m the relahhg to the P l. 576 parts of a commercial polyether, which is initiratwn f polyurethane am. there y a be P ated with glycerin and which consists of m0] porated 1n the foam-forming mixture various additives percent of oxyethylene 70 mo] percent of oxypro such as other surfactants, for example oxyethylated pylene units, with the remainder consisting mostly Phenols, exyethylated fatty aleehols h as oleyl alee' of hydroxyl groups. The polyether has the followhol, fatty acid salts such as diethylamine oleate, suling characteristics; phuric acid derivatives of long chain compounds such as sulphated methyl oleate, and polyalkylene oxide block copolymers, flame-retardants such as, B- g g h 2 2;: 300 trichlorethyl phosphate and antimony oxide, plasticisg g jg ggf app? 01 weight percent 'ers such as tricresyl phosphate and dioctyl phthalate, Water content: no more than 0.1 weight percent antioxidants such as alkylphenols, coloring matters and fillers such as carbon black, mica, and silica and auxili- (This P c iS omm rcially available under the ary gas-forming agents such as lithium aluminum hyname Desmophen 3900.) dride. 2. 18 parts water,

The organopolysiloxanes of this invention may be in- 3. 1 Parts triethaflolamine, corporated with any of the other additives mentioned 6 Parts im hyl an ami above or they may be incorporated separately. Thus 40 30 parts monofluorotrichloromethane and they may be added to the polyether or the polyisocya- 6. 6 parts organosilicon compound. I nate before any reaction occurs or to the polyether- The Components are mixed at 1740 rpm'in a high polyisocyanate prepolymer, or they may be blended shearing stress mixing device (available under the with a mixture of other ingredients such as water and ame Lenart'Rapid") for 60 seconds and then quickly a catalyst, or with for example the flame-retardant. reacted with 342 parts of a mixture consisting of Various embodiments of this invention are further percent by weight of diphenylmethane-p,p'- illustrated in the following examples in which all parts iisocyanate and 40 percent by weight of mixture conare by weightunless otherwise specified. sisting of percent by weight of 2,4- and 20 percent by weight of 2,6-tolylenediisocyanate-isomers and then I EXAMPLE 1 50 processed for 8 seconds at 1740 rpm in the above men- Preparation of Hydrolysates of this Invention tioned mixer.

Ab ut 70 parts f water ar added dr pwi a d The resulting low viscose mixture is then poured in under constant agitation to 21 1 parts of phenyltria box form which is coated with an organopolysiloxane chlorosilane and 432 parts of trimethylchlorosilane l 'i ing nd hardening occur within a short with the evolution of hydrogen chloride. About 200 55 time without additional heat being applied. The resultparts of water are then added quickly. After stirringfor ljg f am have the following characteristics:

TABLE ORGgOSILL EXAMPLE COMPO lJND SURFACE SHRINKAGE FOAM STRUCTURE 2 Example 1 (it) even soft skin none fine & lurgc percent of open cells 3 Example 1 (b) even very soft skin none fine & very large er- I cent of open ce ls 4 Example 1 (c) soft skin some fine. almost I no open cells 5 Y6454"('*) irregular skin considerable very fine. percent closed cells 6 None bubbles under skin coarse cells some (') Y6454 is a commercial organosilicon compound manufactured by Union Carbide Corporation.

Examples 2 and 3 of the above table show that when the organospolysiloxanes of this invention (Examples 1(a) and 1(b)) are added to a polyurethane composition, the resulting foam has a fine cell structure with a large percent of open cells and no shrinkage.

Although specific examples of the invention have been described, it is not intended to limit the invention solely thereto, but to include all the variations and modifications falling within the spirit and scope of the appended claims.

What is claimed is: v

1. An improved method for the manufacture of polyurethane foams from polyethers having on the average at least two hydroxyl groups per molecule and organic diisocyanates, in the presence of organopolysiloxanes, cross-linking agents, catalysts, and blowing agents, the improvement which comprises adding as the organopolysiloxanes, hydrolysates obtained from the hydrolysis of mixtures containing (a) silanes of the general formula R,,SiX and (b) at least 1 mol of silanes of the general formula R SiX per equivalent of X in the silanes (a) where R is a hydrocarbon radical, X is a hydrolyzable group; and n is or 1, said hydrolysates having a boiling point below about 200C. at 0.1 mm Hg '(abs.).

2. The method of claim 1, wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mol ratio of from 1:4 to 1:12.

3. The method of claim 1, wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mol ratio of from 1:6 to 1:10.

4. The method of claim 1 wherein the hydrolysates are separated by distillation from non-distillable components and components having a boiling point higher than 200C. at 0.1 mm Hg (abs.) prior to their use.

5. The method of claim 1 wherein the hydrolysates are separated by distillation from non-distillable com- 200C. at 0.1 mm Hg (abs.) and siloxanes of the formula (R Si) O prior to their use.

6. An improved method for manufacturing a polyurethane foam by the cold foam process from polyethers having an average of at least two hydroxyl groups per molecule and organic diisocyanates in the presence of organopolysiloxanes, cross-linking agents, catalysts, and blowing agents, the improvement which comprises adding as the organopolysiloxanes, hydrolysates containing (a) silanes of the general formula R,,SiX and (b) at least 1 mol of silanes of the general formula R SiX, per equivalent of X in the silanes (a) where R is a hydrocarbon group, X is a hydrolyzable group and n is O or 1, said hydrolysates having a boiling point below about 200C. at 0.1 mm Hg (abs.).

7. The method of claim 6 wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mol ratio of from 1:4 to 1:12.

8. The method of claim 6, wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mo] ratio of from 1:6 to 1:10.

9. The method of claim 6 wherein the hydrolysates are separated by means of distillation from the nondistillable components and components having a boiling point above 200C. at 0.1 mm Hg (abs) prior to their use.

10. The method of claim 1 wherein the hydrolysates accordance with claim 6. 

1. AN IMPROVED METHOD FOR THE MANUFACTURE OF POLYURETHANE FOAMS FROM POLYETHERS HAVING ON THE AVERAGE AT LEAST TWO HYDROXYL GROUPS PER MOLECULE AND ORGANIC DIISOCYANATES, IN THE PRESENCE OF ORGANOPOLYSILOXANES, CROSS-LINKING AGENTS, CATALYSTS, AND BLOWING AGENTS, THE IMPROVEMENT WHICH COMPRISES ADDING AS THE ORGANOPOLYSILOXANE, HYDROLYSATES OBTAINED FROM THE HYDROLYSIS OF MIXTURES CONTAINING (A) SILIANE OF THE GENRAL FORMULA RNSIX4-N AND (B) AT LEAST 1 MOL OF SILIANES OF THE GENERAL FORMULA R3SIX PER EQUIVALENT OF X IN THE SILANES (A) WHERE R IS A HYDROCARBON RADICAL, X IS A HYDROLYZABLE G GROUP; AND N IS 0 OR 1, SAID HYDROLYSATES HAVING A BOILING POINT BELOW ABOUT 200*C. AT 0.1 MM HG (ABS).
 2. The method of claim 1, wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mol ratio of from 1:4 to 1:12.
 3. The method of claim 1, wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mol ratio of from 1:6 to 1:10.
 4. The method of claim 1 wherein the hydrolysates are separated by distillation from non-distillable components and components having a boiling point higher than 200*C. at 0.1 mm Hg (abs.) prior to their use.
 5. The method of claim 1 wherein the hydrolysates are separated by distillation from non-distillable components or components having a boiling point above 200*C. at 0.1 mm Hg (abs.) and siloxanes of the formula (R3Si)2O prior to their use.
 6. An improved method for manufacturing a polyurethane foam bY the cold foam process from polyethers having an average of at least two hydroxyl groups per molecule and organic diisocyanates in the presence of organopolysiloxanes, cross-linking agents, catalysts, and blowing agents, the improvement which comprises adding as the organopolysiloxanes, hydrolysates containing (a) silanes of the general formula RnSiX4 n and (b) at least 1 mol of silanes of the general formula R3SiX, per equivalent of X in the silanes (a) where R is a hydrocarbon group, X is a hydrolyzable group and n is 0 or 1, said hydrolysates having a boiling point below about 200*C. at 0.1 mm Hg (abs.).
 7. The method of claim 6 wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mol ratio of from 1:4 to 1:12.
 8. The method of claim 6, wherein the hydrolysates are mixtures of phenyltrichlorosilane and trimethylchlorosilane in a mol ratio of from 1:6 to 1:10.
 9. The method of claim 6 wherein the hydrolysates are separated by means of distillation from the non-distillable components and components having a boiling point above 200*C. at 0.1 mm Hg (abs.) prior to their use.
 10. The method of claim 1 wherein the hydrolysates are separated from the non-distillable components or components with a boiling point above 200*C. at 0.1 mm Hg (abs.), and siloxanes of the formula (R3Si)2O prior to their use.
 11. A cellular polyether-urethane foam prepared in accordance with claim
 1. 12. A cellular polyether-urethane foam prepared in accordance with claim
 6. 